Attach geometry to other geometry without duplicating it
You hit on the first one which is using separate.

Once you move the separated object into place (you can control this with extreme accuracy if you are using snapping methods for vertices / edges in this particular case), you can use JOIN.

To use the command:


Select the pyramid textured cross.
While holding SHIFT select the extruded cross shape.
Finally CTRL + J will perform the join operation.


To clean up the operation:


TAB To enter into Edit Mode.
A To Select all Vertices.

a. NOTE: CTRL + TAB >> V if your selection mode is NOT set to Vertex.
W >> R to remove redundant vertices.